1. Field of Invention
This invention relates to a manufacturing method of a tool used in an integrated circuit (IC) process, and more particularly to a method of manufacturing a photomask and a method of repairing an optical proximity correction (OPC) to the graphic data of a photomask.
2. Description of Related Art
After the linewidth of IC process drops to the deep sub-micro level, the control on the critical dimension (CD) of each patterned layer of an integrated circuit becomes more and more important. When the linewidth drops to one half or less of the wavelength of the light source for exposure, optical proximity correction is required for the patterns of the photomask to reduce the deviation of the critical dimension. The optical proximity correction includes, for example, adding serifs or a hammerhead at an end of a bar-like pattern, making protrusions and indents at the edges of a pattern, adding an assist line beside a pattern, and so forth.
In the conventional method of manufacturing a photomask with OPC, an OPC recipe is applied to correct the patterns in the graphic data of the photomask after the graphic patterns are provided, and then the graphic data with OPC is subjected to a process rule check (PRC), which utilizes computer simulations to predict whether the patterns transferred onto the wafer meet the requirements of the process or not. If one or more patterns cannot pass the process rule check, another OPC recipe is applied to correct all patterns in the original graphic data, and then another process rule check is performed. However, for the graphic data system (GDS) file of a photomask used in advanced IC processes easily has a size up to hundreds of gigabytes, the conventional method is quite time-consuming.